JPH05119282A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To obtain high diffraction efficiency even in the case of P polarization as well as S polarization and to facilitate peeling at the time of duplication by passing laser light through a hologram twice and making the ratio (lambda/d) of the wavelength lambda of the laser light and the pitch intervals (d) of a hologram diffraction grating small on each-time passage. CONSTITUTION:Although one hologram is conventionally manufactured, two holograms are divisionally manufactured and the lambda/d when the laser light passes them each once is set to 0.4-1.1. On this hologram rotary disk 10, laser light which is made incident on one surface of the substrate is diffracted by the 2nd hologram H2 first, diffracted by the 1st hologram H next, and projected from the other surface of the substrate. Further, the lambda/d of the 1st hologram H1 is, for example, 0.7, so the diffraction efficiency which is almost as high as that of the P polarization is obtained even by the P polarization. Further, the 2nd hologram H2 is so constituted that lambda/d=0.7, so the high diffraction efficiency which is similar to that of the 1st hologram is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device, and more particularly to a light beam scanning device for scanning a laser beam using a hologram.

[0002]

2. Description of the Related Art Laser scanners used in OA equipment such as laser printers and laser fax machines, laser drawing devices, laser inspection devices, etc. have hitherto been known as rotary polygon mirrors and f.
A combination with a -θ lens is used. However, in this method, it is difficult to reduce the cost because the rotary polygon mirror requires high processing accuracy and the f-θ lens requires a combination of many lenses. On the other hand, the hologram scanning device using the hologram can be mass-produced by duplication, and thus the cost reduction can be expected.

FIG. 1 shows the applicant's prior application (Japanese Patent Application No. 3-629).
No. 61) shows an example of the hologram scanning device. In FIG. 1, 3 is a photosensitive drum, 4 is an image plane on the surface thereof, 5 is an incident wave of laser light, 6 and 7 are diffracted waves, and 10 is a high speed formed by arranging a plurality of holograms H (FIG. 4). A hologram rotating plate that rotates at 20; a hologram stationary plate 20; M1 a rotating direction of the hologram rotating plate 10;
Reference numeral 2 denotes a rotation direction of the photosensitive drum 20, M3 denotes a main scanning direction by laser light, and H denotes a hologram. In this hologram scanning device, laser light (incident wave 5) from a semiconductor laser (not shown) is incident on a hologram rotating plate 10 rotating at high speed in the M1 direction to scan this laser light, and this hologram rotating plate A hologram stationary plate 20 for linearly scanning the laser beam (diffracted wave 6) scanned by 10 as shown by M3 and keeping the scanning speed constant.
Via the image forming surface 4 of the photosensitive drum 3 which rotates in the direction M2.
It has a configuration that converges upward.

FIGS. 2A and 2B show a configuration of the hologram rotating plate 10 for compensating for the position variation of the scanning line due to the parallelism of the substrate. In FIG. 2, 3 is a photosensitive drum, 5 is an incident wave, 6 and 7 are diffracted waves, 10 is a hologram rotating plate, 20 is a hologram stationary plate, M3 is a main scanning direction, M4 is a sub scanning direction, and H is a hologram. .. As the light beam 5 incident on the hologram rotating plate 10, a light beam that converges in the sub-scanning direction (M4) orthogonal to the main scanning direction (M3) is used. At this time, the ratio λ / d between the wavelength of the laser light and the pitch interval of the hologram diffraction grating is 1.4.
~ 1.5. Note that Japanese Patent Application No. 3-62961 should be referred to for the details of the configuration for compensating the positional fluctuation of the scanning line.

FIG. 3A shows hologram diffraction efficiency when a surface relief type hologram that is easy to copy is used as a hologram (APPLIED OPTICS Vol. 3, No. 14, 2303-2).
310 (1984)). Figure 3 shows the hologram diffraction efficiency.
As shown in (a), it depends on λ / d, and the tendency is so-called S-polarized light in which the grating direction and the direction of the linearly polarized light coincide, and so-called P-polarized light in which the grating direction and the direction of the linearly polarized light are vertical. You can see that they are different. Therefore, as is clear from FIG. 3A, λ / d
= 1.4 to 1.5, it is understood that S-polarized light must be used to increase the diffraction efficiency. 3 (b) shows the cross section of the hologram, d is the pitch interval of the hologram diffraction grating, and h is the height of the cross section of the rotary grating.

FIG. 4A shows the case where the polarization direction of the semiconductor laser L which is the light source is parallel to the direction of the grating, and FIG. 4B shows the polarization direction and the direction of the grating of the semiconductor laser which is the light source. Is vertical. In FIGS. 4A and 4B, 10 is a hologram rotating plate, L is a semiconductor laser which is a light source, and H is a hologram. In the case of irradiating the beam so as to converge in the sub-scanning direction, in FIG. 4A, the semiconductor laser L has a short aperture diameter in the polarization direction, so that the loss of light intensity increases. On the other hand, when the light enters as shown in FIG. 4B, the direction in which the aperture diameter is short, that is, the polarization direction is parallel to the sub-scanning direction,
The loss of incident light intensity is greatly reduced. However, in this case, so-called P-polarized light, in which the grating direction and the polarization direction are perpendicular to each other, is obtained, and as can be understood from FIG.

As a means for solving this problem, there is a method of inserting a half-wave plate (λ / 2 plate) behind the semiconductor laser L and rotating the polarization plane of the laser light by 90 °. However, there is a disadvantage in that the cost becomes high because the λ / 2 plate is required. Also, when replicating a surface relief hologram, if the gap between the gratings is small, it may be difficult to separate the stamper from the substrate.

[0008]

As described above, in the light beam scanning device using the hologram, the hologram diffraction efficiency depends on the ratio λ / d between the laser light wavelength and the pitch interval of the hologram diffraction grating, and The so-called S-polarized light and P-polarized light are very different. Therefore, in the present invention, the laser light is passed through the hologram twice,
Reduce λ / d for each pass (eg 0.4 ≦
λ / d ≦ 1.1) so that the so-called P-polarized light can obtain the same high diffraction efficiency as that of the S-polarized light, and the light beam scanning can be easily performed at the time of replication. The purpose is to provide a device.

[0009]

In order to solve such problems, according to claim 1, as shown in FIG. 7 or 11, laser light (5) is applied onto a transparent substrate (10). The hologram (H1, H2) thus produced is configured to pass through twice, and the ratio (λ /) between the wavelength (λ) of the laser beam and the pitch interval (d) of the hologram diffraction grating when passing once each time.
There is provided a light beam scanning device characterized in that d) is in the range of 0.4 to 1.1.

According to the second aspect, as shown in FIG. 7, holograms (H1, H2) are prepared on both surfaces of the transparent substrate (10) so that the laser beam is diffracted once by each hologram. A light beam scanning device according to claim 1 is provided. According to claim 3, as shown in FIG. 11, the hologram (H) is formed on one surface of the transparent substrate (10) and the mirror (M) is formed on the other surface.
Laser beam diffracted by the hologram surface (H) is reflected by the mirror (M), and the same hologram surface (H) is produced.
The optical beam scanning device according to claim 1, wherein the optical beam scanning device is configured to diffract light again.

According to a fourth aspect of the present invention, there is provided the light beam scanning device according to the second or third aspect, wherein the substrate on which the hologram is formed is used as the hologram rotating plate (10). According to claim 5, there is provided the light beam scanning device according to claim 2 or 3, characterized in that a substrate on which a hologram is produced is used as a hologram stationary plate (20).

According to claim 6, as shown in FIGS. 1, 7 and 11, one hologram plate having holograms formed on a transparent substrate is constituted as a rotating plate (10), and holograms are produced on the transparent substrate. The other hologram plate that was
0), the laser beam (5) is incident on the hologram rotating plate (10) so as to be converged in the sub-scanning direction (M4) orthogonal to the scanning direction (M3), and the hologram rotating plate (10) is In the light beam scanning device, the diffracted light (6) diffracted by 10) is incident on the hologram stationary plate (20), and the diffracted light (7) is converged on the image plane (4) for scanning. Laser beam (5) is incident on the hologram rotating plate (10) so that the polarization direction of the rotating plate is perpendicular to the grating direction of the scanning center.
Laser light (5) incident on (0) is a hologram (H1, H2) produced on a transparent substrate constituting the rotating plate (10).
Is passed twice, and the ratio (λ / d) between the wavelength (λ) of the laser beam and the pitch interval (d) of the hologram diffraction grating when passing once each is 0.4 to 1. There is provided a light beam scanning device characterized by being within the range of 1.

According to claim 7, as shown in FIG. 6, the hologram (H1) on one surface of the rotating plate (10) is an aberration formed by a plane wave perpendicular to the substrate and a first predetermined angle (θ1). And a hologram (H2) on the other surface of the rotating plate is composed of a plane wave perpendicular to the substrate and a second predetermined angle (θ2) different from the first predetermined angle (θ1). The light beam scanning device according to claim 6, wherein the light beam scanning device is manufactured by using a wave having an aberration.

According to the eighth aspect, as shown in FIG. 8, the hologram (H1) on one surface of the rotating plate (10) is provided with a third hologram.
Of the plane wave having the predetermined angle (θ3) and the wave having the aberration having the first predetermined angle (θ1), and the hologram (H2) on the other surface of the rotating plate is formed by the third predetermined angle. 7. The light beam scanning device according to claim 6, wherein the light beam scanning device is made of a plane wave composed of (θ3) and a plane wave composed of a second predetermined angle (θ2) different from the first predetermined angle (θ1). To be done.

According to the ninth aspect, as shown in FIG. 9, the hologram (H1) on one surface of the rotating plate (10) is formed into a fourth hologram.
Of a diverging spherical wave having a predetermined angle (θ4) and a predetermined focal length (F) and a wave having an aberration having a first predetermined angle (θ1), and a hologram on the other surface of the rotating plate. (H2) is a convergent spherical wave having a third predetermined angle (θ3) and a predetermined focal length (F) and a plane wave having a second predetermined angle (θ2) different from the first predetermined angle (θ1). A light beam scanning device according to claim 6, which is manufactured.

According to the tenth aspect, as shown in FIG. 10, the hologram (H) is formed on one surface of the transparent substrate constituting the rotating plate (10) and the mirror (M) is formed on the other surface. 7. The light according to claim 6, wherein the laser light diffracted by the hologram surface (H) is reflected by the mirror (M) and further diffracted again by the same hologram surface (H). A beam scanning device is provided.

[0017]

According to the present invention, the laser beam passes through the hologram twice, and λ / d can be reduced each time it passes once (for example, 0.4 ≦ λ / d ≦ 1.1). Even in the case of so-called P-polarized light, it is possible to maintain the same high diffraction efficiency as that of S-polarized light, and it is possible to prevent a decrease in the amount of light on the image plane. Further, since the spatial frequency of the hologram can be significantly reduced, it is possible to easily separate the stamper and the substrate when the hologram is duplicated.

[0018]

EXAMPLE First, FIG. 5 shows a conventional hologram manufacturing method. In FIG. 5, 10 is a hologram rotating plate, 12 is a cylindrical lens, and O is the rotation center of the hologram rotating plate 10. In this example, a wave having an aberration that diverges in the sub-scanning direction is used as the object wave, and a plane wave is used as the reference wave, and the incident angles of the object wave and the reference wave are θ1 and θ2, respectively. The object wave is exposed on the substrate through the cylindrical lens 12.

In the above known example, for example, θ1 = 24.76 °,
θ2 = 23.44 °, fabrication wavelength λ1 = 441.6nm, reproduction wavelength λ
When 1 = 785.0 nm, the λ / d of the hologram on the hologram rotating plate is 1.4. In this case, it is clear from FIG. 3 that high diffraction efficiency cannot be obtained with so-called P-polarized light. In order to obtain a high diffraction efficiency even with P-polarized light, it is sufficient to reduce λ / d to about 0.8.

As one of the means, FIG. 6 shows a hologram manufacturing method according to the first embodiment of the present invention. In FIG. 6, 10 is a hologram rotating plate, 12 is a cylindrical lens, O is the center of rotation of the hologram rotating plate 10, and H1,
H2 is a hologram. In this embodiment, the hologram which was conventionally one sheet is separately produced into two pieces. First
On one side of the hologram transparent substrate,
An interference fringe is formed by a plane wave (reference wave 1) perpendicular to the substrate and a wave having an aberration (object wave 1) incident at an angle θ1. Next, a second hologram is provided on the other surface of the hologram transparent substrate surface with a plane wave (reference wave 2) perpendicular to the substrate,
An interference fringe is formed by a wave (object wave 2) having an aberration that is incident at an angle θ2 different from the angle θ1. By producing these two holograms on both surfaces of a transparent substrate such as glass as described above, as shown in FIG. 7, the same function as that of a conventional hologram rotating plate in which only one hologram H is produced is obtained. It is possible to manufacture a hologram rotating plate having the same.

That is, in the hologram rotating plate of this embodiment, the laser light incident from one surface of the substrate is first diffracted by the second hologram (H2) and then by the first hologram (H1). The light is emitted from the other surface of the substrate.
Moreover, since λ / d of the first hologram (H1) is 0.7, as is clear from FIG. 3, it is possible to obtain the same high diffraction efficiency for both P-polarized light and S-polarized light. Since the hologram (H2) of 2 also has λ / d = 0.7,
It is possible to maintain the same high diffraction efficiency as that of the first hologram. From the above, as shown in FIG. 7, it has the same function as a conventional hologram rotating plate, and it is possible to obtain high diffraction efficiency even with so-called P-polarized light. Further, since the hologram rotating plate of this embodiment can be easily duplicated from both sides of a transparent substrate such as glass, it is suitable for mass production and cost reduction can be expected.

FIG. 8 shows a hologram manufacturing method according to the second embodiment of the present invention. The hologram manufacturing method is the same as that of the first embodiment, but the reference waves (1) and (2) that are plane waves are used.
Is different from the first embodiment only in that the exposure is performed by inclining by the same angle (θ3). In the second embodiment, by changing the incident angle (θ3) of the reference waves (1) and (2), the alignment of the optical components can be facilitated during hologram exposure.

FIG. 9 shows a hologram manufacturing method according to the third embodiment of the present invention. In this embodiment, the reference wave (1) is a divergent spherical wave that is incident at a focal length F and a predetermined angle (θ4). The reference wave (2) is a convergent spherical wave that is incident at the same focal length F and at the predetermined angle (θ4). In the third embodiment, by appropriately changing the focal length (F) or the incident angle (θ4), it is possible to easily align the optical components during hologram exposure.

FIG. 10 shows a hologram manufacturing method according to the fourth embodiment. This is different from the above embodiment in that light passes through one hologram twice. That is, as with the first hologram H1 described in the first embodiment, a plane wave (reference wave) perpendicular to the substrate is formed on one surface of the hologram transparent substrate.
And a wave (object wave) having an aberration that is incident at an angle θ1 form a hologram H, and on the opposite side thereof, a mirror M is formed by aluminum vapor deposition or the like without forming a hologram. To form. Since λ / d in the hologram H is 0.7 in this hologram rotating plate, it is possible to obtain a diffraction efficiency similar to that of S-polarized light even with P-polarized light.

11 (a) and 11 (b) are views for explaining the action of the hologram plate of the fourth embodiment shown in FIG. 10 in comparison with a conventional hologram plate. As shown in FIG. 11B, the light diffracted by the hologram H on one surface of the substrate is reflected by the mirror M formed on the other surface of the substrate and diffracted again by the same hologram H, so that λ / d = It is 0.7, and high diffraction efficiency can be obtained.

FIGS. 12A and 12B show a hologram manufacturing method according to the fifth embodiment. As shown in FIG.
When the spatial frequency of the hologram stationary plate 20 is high, the substrate is long, and thus it may be difficult to separate the stamper and the substrate when copying. At this time, as shown in FIG. 12B, a new reference wave (for example, a plane wave orthogonal to the substrate surface)
Then, a hologram was prepared in the same manner as in the above example, and λ
By reducing / d, the stamper and the substrate can be easily separated.

[0027]

As described above, according to the present invention, even in the case of so-called P-polarized light, it is possible to maintain the same high diffraction efficiency as that of S-polarized light, and it is possible to prevent a decrease in the amount of light on the image plane.
Further, since the λ / 2 plate is unnecessary, the cost can be reduced. Further, the spatial frequency of the hologram can be reduced to about half, and the stamper and the substrate can be easily separated from each other during copying.

[Brief description of drawings]

FIG. 1 shows an example of a hologram scanning device proposed by the applicant in a prior application (Japanese Patent Application No. 3-62961).

2A and 2B are diagrams of a hologram rotating plate 10, FIG.
6 illustrates a configuration for compensating for a position variation of a scanning line due to parallelism of a substrate.

FIG. 3A shows a hologram diffraction efficiency when a surface relief type hologram that is easy to duplicate is used as a hologram, and FIG. 3B shows a cross section of the hologram.

FIG. 4A shows a case where the polarization direction of a semiconductor laser L, which is a light source, is parallel to the grating direction,
(B) shows the case where the polarization direction of the semiconductor laser as the light source and the direction of the grating are orthogonal to each other.

FIG. 5 shows a conventional hologram manufacturing method.

FIG. 6 shows a method of manufacturing a hologram according to the first embodiment of the present invention.

7A and 7B show the operation of the hologram according to the first embodiment of the present invention in comparison with a conventional hologram, FIG. 7A showing a conventional example, and FIG. 7B showing the case of the first embodiment of the present invention. Show.

FIG. 8 shows a hologram manufacturing method according to a second embodiment of the present invention.

FIG. 9 shows a hologram manufacturing method according to a third embodiment of the present invention.

FIG. 10 shows a hologram manufacturing method according to a fourth embodiment of the present invention.

11A and 11B are views for explaining the action of the hologram plate of the fourth embodiment shown in FIG. 10 in comparison with a conventional hologram plate.

12A and 12B show a hologram manufacturing method according to a fifth embodiment.

[Explanation of symbols]

 3 ... Photosensitive drum 4 ... Image plane 5 ... Incident wave 6, 7 ... Diffraction wave 10 ... Hologram rotation plate 12 ... Cylindrical lens 20 ... Hologram stationary plate O ... Rotation center of hologram rotation plate H, H1, H2 ... Hologram M ... mirror

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keikazu Aritake 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (9)

[Claims] 1. A laser beam (5) is configured to pass through a hologram (H1, H2) formed on a transparent substrate (10) twice, and the wavelength of the laser beam when passing once each ( A light beam scanning device, characterized in that a ratio (λ / d) between the λ) and the pitch interval (d) of the hologram diffraction grating is within a range of 0.4 to 1.1. 2. The hologram (H1, H2) is produced on both surfaces of the transparent substrate (10), and the laser light is diffracted once by each hologram. Light beam scanning device. 3. A hologram (H) is formed on one surface of a transparent substrate (10), a mirror (M) is formed on the other surface, and laser light diffracted by the hologram surface (H) is reflected by the mirror (M). ), And further diffracts again on the same hologram surface (H).
The light beam scanning device according to. 4. The hologram-made substrate is used as a hologram rotating plate (10).
Alternatively, the light beam scanning device according to item 3. 5. A substrate on which a hologram is produced is used as a hologram stationary plate (20).
Alternatively, the light beam scanning device according to item 3. 6. A hologram plate formed on a transparent substrate is configured as one hologram plate as a rotating plate (10), and another hologram plate formed on a transparent substrate is configured as a stationary plate (20) in the scanning direction ( The laser beam (5) is incident on the hologram rotating plate (10) so as to be converged in the sub-scanning direction (M4) orthogonal to the direction M3), and the diffracted light (diffracted by the hologram rotating plate (10) ( 6)
In the hologram stationary plate (20), the diffracted light (7) is converged on the image plane (4) and scanned, and the polarization direction of the laser light is perpendicular to the grating direction of the scanning center. Laser beam (5) is incident on the hologram rotating plate (10) so that the laser beam (5) is incident on the rotating plate (10).
0) holograms (H1,
H2) is passed twice, and the ratio (λ / d) between the wavelength (λ) of the laser light and the pitch interval (d) of the hologram diffraction grating when passing once each is 0.4 to. 1. A light beam scanning device characterized in that it is within the range of 1.1. 7. A hologram (H1) on one surface of a rotating plate (10) is made of a plane wave perpendicular to a substrate and a wave having an aberration of a first predetermined angle (θ1), or Three
Of a plane wave having a predetermined angle (θ3) and a wave having an aberration having a first predetermined angle (θ1), and a hologram (H2) on the other surface of the rotating plate is a plane wave perpendicular to the substrate. And a wave having an aberration of a second predetermined angle (θ2) different from the first predetermined angle (θ1), or a plane wave having the third predetermined angle (θ3) and a first predetermined angle (θ3). 7. The light beam scanning device according to claim 6, wherein the light beam scanning device is manufactured with a plane wave having a second predetermined angle (θ2) different from the angle (θ1). 8. A hologram (H1) on one surface of a rotating plate (10) is provided with a diverging spherical wave having a fourth predetermined angle (θ4) and a predetermined focal length (F) and a first predetermined angle (θ1). )
And a convergent spherical wave having a third predetermined angle (θ3) and a predetermined focal length (F), and a hologram (H2) on the other surface of the rotating plate. 7. The light beam scanning device according to claim 6, wherein the light beam scanning device is manufactured with a plane wave having a second predetermined angle (θ2) different from the predetermined angle (θ1). 9. A laser diffracted on a hologram surface (H) by forming a hologram (H) on one surface of a transparent substrate constituting a rotating plate (10) and a mirror (M) on the other surface. 7. The light beam scanning device according to claim 6, wherein the light is reflected by the mirror (M) and is diffracted again by the same hologram surface (H).